1. Field of the Invention
The current invention concerns the art of portable light sources and, more specifically, a thin, planar, bright disposable flashlight.
2. Description of Related Art
The history of the flashlight goes back almost to the invention of the electric incandescent lamp. The electric lamp made possible a portable light source that was immune to wind currents that would extinguish a candle and was compact and cool to the touch, unlike oil or carbide lanterns.
A typical prior art flashlight 10 is shown in FIG. 1. The unit comprises a cylindrical body 12 for containing dry cell batteries 11. The batteries 11 are normally arranged in a series configuration because the 1.5 volts provided by a typical battery is generally inadequate to produce a sufficiently bright light. A lamp 13 is in contact with one terminal of the battery 11, while a switch 14 regulates operation of the lamp 13 by completing an electrical circuit between a second battery terminal and the lamp 13. To increase the effective brightness of the flashlight 10 by focusing the output light in a small beam, the lamp 13 is surrounded by a reflector 15 which is protected by a clear lens 16.
The typical flashlight is ideal for emergency use since it can be conveniently stored in a cupboard or a drawer and, thus, be available to provide light when normal electric power fails as during a storm or earthquake. Of course, if the flashlight is sufficiently small and inexpensive, units can be left at a number of locations where a portable light is occasionally of great use (i.e., in the glove compartment of an automobile, by an electric fuse panel in a basement, inside a garage cupboard or similar unlighted storage area).
However, flashlights are frequently bulky, particularly if several dry cell batteries are included in a series arrangement (usually end to end) to provide power for an especially bright lamp. The sheer bulk and length of multiple battery flashlights tends to make it difficult to stow a bright flashlight in a coat pocket or other convenient location. Miniature flashlights which contain only one or two miniature dry cell batteries have been produced, but they are typically less bright than a full size flashlight and also tend to have a fairly brief period of operation before the light dims and the dry cells must be replaced.
There have been a number of bright miniature flashlights produced through the use of special light bulb technologies such as krypton or halogen lamps manufactured to center the lamp's filament, thereby facilitating the focusing of the flashlight's beam. However, such miniature flashlights are often expensive, both because of the special lamps, and because of the machining costs of the miniature flashlight body. Their high cost tends to mitigate against the deployment of numerous flashlights for emergency use.
Another problem with traditional flashlights, particularly when they are stowed in numerous locations for possible emergency use, is that the dry cell batteries lose power with age and/or leak, damaging the expensive flashlight body. Therefore, if a number of conventional flashlights are to be deployed for future emergency use, it is necessary to check them fairly frequently and replace the dry cell batteries before any damage from leaking batteries occurs.
There have also been some efforts to deal with the bulk of flashlights by arranging the batteries in a side-by-side configuration. This produces a flashlight of an overall rectangular configuration. Such a unit is more likely to fit into a purse or pocket, but the thickness of ordinary dry cell batteries requires that the rectangular flashlight be relatively bulky. For example, rectangular flashlights designed to operate on side-by-side AA batteries are generally almost an inch thick.